When debugging integrated circuits, it may be advantageous to be able to observe internal analog nodes during operation. Bringing out the internal nodes to pads may not provide useful diagnostic capabilities, however, due to the loading effect of wires and pads on the internal nodes, which may be sensitive to such loading. Circuits may be implemented in an integrated circuit to sample or amplify the signals from such nodes, before bringing the resulting signals to the exterior of the chip. Such circuits, however, may themselves load the nodes being sensed to an unacceptable extent, and they may consume unacceptable amounts of chip area or unacceptable amounts of operating power.
Thus, there is a need for a small on-chip oscilloscope that can be instantiated multiple times, requiring little chip area, and consuming little power.